KEY TO THE SPECIES VU 



tated the use of many ; therefore, one or more dictionaries, or 

 manuals containing glossaries, ought to be always at hand. 

 (4) That it is always well to have one or more copies of the 

 standard manuals at hand for reference (Coulter's is the only 

 one out at present devoted to this region in particular, though 

 many of our species will be found in Gray's and in Britton's). 



Lastly, I wish to atsknowledge my indebtedness to the first 

 in this series of Keys, viz., that prepared by Dr. Coulter for the 

 Eastern United States. In so far as the species used are the 

 same for the two regions, I have taken the liberty of adopting 

 not only the same mode of treatment, but in many instances 

 the descriptions in their entirety. I am further deeply in- 

 debted in many ways to Dr. Britton's recent Manual and to 

 Dr. Coulter's Manual of the Rocky Mountains. 



AvEN Nelson. 

 Univeksitt of Wyoming, 

 Laramie, March, 190S. 



